Modeling species density for conservation through integrating occupancy and telemetry data

Background/Question/Methods

It is often highly desirable to know not only where species are likely to occur (i.e., occupancy) but also how many individuals are supported by a given habitat (i.e., density). For many animals, occupancy and density are likely determined by separate and distinct ecological processes. Here, we model expected density on a landscape as the product of a landscape-scale occupancy probability and a habitat-scale density given occupancy. One can conceptualize our modeling process as fully packing a landscape with home ranges based on habitat quality, and then subtracting home ranges based on a probabilistic process that accounts for the fact that heterogeneous landscapes are rarely at maximum density (e.g., due to elevation, latitude, etc.). 

Results/Conclusions

We develop and apply this model to the Black-backed Woodpecker (Picoides arcticus) in California, a species of conservation concern. Occupancy is derived from a regional monitoring effort, while density given occupancy comes from a telemetry study of home-range size variation. Both models are combined to interpolate expected density of Black-backed Woodpeckers within the 400 sq mile Rim fire which burned in 2013. The resultant model provides a critical tool for resource managers to understand trade-offs in preserving area for burned forest habitat versus managing for other post-fire goals. Our model also outlines a potential method for modeling density beyond simple occupancy for other rare and elusive species.